[2133] Fix NPE in Related Elements view

Since #2032, `self` is a single element, not a list.

Bug: #2133
Signed-off-by: Pierre-Charles David <pierre-charles.david@obeo.fr>
Signed-off-by: Axel RICHARD <axel.richard@obeo.fr>

CHANGELOG.adoc

@@ -35,6 +35,7 @@ An absent/empty candidates expression now simply means the widget is empty.
 - https://github.com/eclipse-sirius/sirius-components/issues/2067[#2064] [view] Enable completion support and other text field customizations for custom widgets
 - https://github.com/eclipse-sirius/sirius-components/issues/2092[#2092] [form] Fix support for help expressions on the _FlexboxContainer_ widget
 - https://github.com/eclipse-sirius/sirius-components/issues/2088[#2088] [tree] Fix initial value of the tree filter bar
+- https://github.com/eclipse-sirius/sirius-components/issues/2133[#2133] [workbench] Fix NPE in Related Elements view
 
 === New Features
 

packages/sirius-web/backend/sirius-web-services/src/main/java/org/eclipse/sirius/web/services/relatedelements/DefaultRelatedElementsDescriptionProvider.java

@@ -62,9 +62,6 @@ public FormDescription getFormDescription() {
 
         // @formatter:off
         Function<VariableManager, String> targetObjectIdProvider = variableManager -> variableManager.get(VariableManager.SELF, Object.class)
-                .filter(self -> self instanceof List<?>)
-                .map(self -> (List<?>) self)
-                .flatMap(self -> self.stream().findFirst())
                 .map(this.objectService::getId)
                 .orElse(null);